Deliciously Frozen Probiotics—Ice Cream and Beyond

Given a choice between cultured buttermilk or a bowl of ice cream, most Americans would choose the latter. Buttermilk may be a healthier option, because it feeds us friendly bacteria that fortify our digestive system, but ice cream is infinitely more satisfying—even if we perceive it to offer us mostly flavor and calories.

Adding probiotic bacteria to ice cream and frozen desserts removes potential guilt and gives us reason to enjoy our favorite scoop. But for the manufacturer, adding these microscopic organisms requires a little know-how.

Probiotics: It’s alive

National Yogurt Association, McLean, VA, notes that probiotics are living microorganisms, which upon ingestion in sufficient number, exert health benefits beyond basic nutrition. “Probiotics need to be viable in order to have any nutritional value, and thus must be incorporated post-pasteurization," says Peggy Pellichero, senior food technologist—dairy team leader, David Michael & Co., Philadelphia. “Interestingly enough, the freezing process does not kill the organisms, it just puts them into a dormant state until consumed."

While the probiotics must be added after pasteurization so they won’t be killed by high temperature, there isn’t consensus as to which step they should be incorporated. “We generally recommend that they be added at the flavor vat," says Jon Hopkinson, Ph.D., senior applications scientist—frozen desserts, Danisco USA, New Century, KS. “Flavoring should not be added at exactly the same time, as concentrated flavors can damage the probiotic cell. Further, it would be good practice to avoid excessive mixing or air incorporation into the mix." Shear and oxygen exposure during manufacture can impact the survivability of probiotic organisms.

According to Mike Bush, vice president of business development, Ganeden Biotech, Inc., Mayfield Heights, OH, the most important part of the formulation process is finding the best possible way to add the probiotic within the manufacturing process where the highest amount of cell survival can be demonstrated.

“Because probiotic organisms can be extremely fragile, they need to be protected from extremes ranging from temperature and pH to pressure and rapid environmental shifts," says Bush. “One of the issues in manufacturing frozen products is the shift in temperature from cold to frozen. Many times, there are large losses when temperature shifts from the mixing temperature to freezing temperatures, and such shifts make many such applications cost-prohibitive."

Probiotics generally survive well in ice cream and frozen desserts, but care is needed. “Anything that can affect the formation of ice crystals in ice cream can affect the bacteria," cautions Hopkinson. “Slow hardening and heat-shock cycles can, therefore, affect the viability of the probiotics. In resale mixes that are frozen for distribution, it is very important that the freezing process be as fast as possible for the same reason."

The pH of the frozen dessert is important. “It would seem counterintuitive in light of recent frozen yogurt popularity, but very low pH product should be avoided," Hopkinson continues.

Bush notes that, since traditional probiotics tend to be more fragile than spore-forming strains, sometimes they require an extra step or change to the manufacturing process to increase viability. “The spore-forming probiotics do not require this," he says.

Spore-forming probiotics are hardier than other probiotics. “The use of such spore-forming organisms eliminates many of the inherent limitations found with non-spore-forming organisms and make difficult applications possible," Bush says. “For example, in frozen applications, the Bacillus coagulans spores simply remain dormant and are very stable through the end of the shelf life of the finished product." The company offers a strain of B. coagulans that is a spore-forming bacterium, meaning it builds a hardened structure inside the cell that protects the cell’s genetic material from extreme temperatures, pressure and low pH.

Lactic acid bacteria are among the hardiest of the non-spore-formers, because they naturally produce a protective layer of exo-polysaccharides. However, these secretions don’t completely envelop the bacteria, so they are only partially shielded.